List Open Tabs

We are planning to deprecate the use by Firefox add-ons of the techniques described in this document.

Don't use these techniques to develop new add-ons. Use WebExtensions instead.

If you maintain an add-on which uses the techniques described here, consider migrating it to use WebExtensions instead.

Add-ons developed using these techniques might not work with multiprocess Firefox (e10s), which is already the default in Firefox Nightly and Firefox Developer Edition, and will soon be the default in Beta and Release versions of Firefox. We have documentation on making your add-ons multiprocess-compatible, but it will be more future-proof for you to migrate to WebExtensions.

Note: to get this working, you will need to save an icon for the button to your add-on's "data" directory as "icon-16.png". You can download the icon here: .

Run the add-on, load a couple of tabs and click the button. You'll see output in the command line console that looks something like this:

info: http://www.mozilla.org/en-US/about/
info: http://www.bbc.co.uk/

You don't get direct access to any content hosted in the tab. To access tab content, you need to attach a script to the tab using tab.attach(). This add-on attaches a script to all open tabs. The script adds a red border to the tab's document: